Technical Field
The present disclosure relates generally to the field of image compression and transmission and more particularly to systems and methods for determining sensitivity of image signals to compression.
Related Art
Only a decade ago, high definition (HD) was cutting-edge video technology. With HD came new wider 16:9 aspect ratio flat screen TVs that made the living room stylish in a way that CRTs could not match. Consumers quickly adopted the new technology and studios, programmers, cable, telco, and satellite video providers rapidly began delivering the user-desired, HD content. HD is now readily available in many forms across multiple platforms.
Recently, Ultra HD (UHD), with at least 4 times as many pixels as HD, has become mainstream. In addition to and along with UHD, a new wave of television viewing options are becoming readily available. The internet has become a rival of legacy managed television distribution pipes. Over-the-top (OTT) bandwidth is now often large enough to support 4k UHD however it can place significant demands on infrastructure. New compression technologies such as HEVC are now available to make better use of video distribution channels since television itself is no longer confined to the home. Every tablet, notebook, PC, and smartphone now has a part time job as a TV screen; and more and more of those evolved-from-computer TVs have pixel density and resolution to rival dedicated TV displays.
Despite the advent of 4k HD technology, the market is still dominated by SD and HD technology displays that would not benefit from the delivery of 4k UHD signals. Moreover, infrastructure limitations may restrict the ability of content providers to deliver 4k UHD signals to end-user devices. Thus, delivery of superior 4k UHD signals may not have any impact on some end-user experiences.
4k UHD is still new enough in the studios and post-production houses that 4k-capable cameras, lenses, image sensors, and downstream processing are still being optimized and thus we cannot be sure that the optics and post processing are preserving every bit of “4k” detail. For content providers and end-users, video compression and multi-bitrate adaptive streaming protocols can change the amount of visual detail to a form that does not preserve true “4k” detail. Thus, determining appropriate compression levels for video to preserve a desired minimum level of detail (SD, HD, UHD or future-developed standards) to be sure that content providers do not over compress and turn high-quality video into something less impressive is extremely important.
Examination of 4k UHD images, reveals that several test sequences that appeared normal to the eye turned out to have unusual properties when examined mathematically. Thus, examination and evaluation of content based upon current, known evaluation techniques could lead to incorrect conclusions related to 4k UHD images and required bandwidth for services.
What is needed is a system and method to appropriately determine compressibility of images such that desired resolutions are delivered to an end users. Additionally, what is needed is a system and method to optimize compression of a video signal based upon bandwidth limitations and/or desired resolution of a delivered video signal.